Since Rick Perry's 50 seconds of tongue-tied agony in Wednesday night's Republican presidential debate, argument has raged about just how bad Perry's "brain fart" was compared with the famous campaign flubs of the past.

But the worst ever? Since Bush won his presidential elections his "misunderestimates" didn't do him much harm. Ford did of course lose in 1976 but it wasn't a happy year for Republicans in the wake of Watergate.

Indeed the closest campaign brain freeze to Perry's came from Arizona governor Jan Brewer in 2010, when she couldn't even make it through her opening statement without blanking. Sadly, it was merely a blip on her road to re-election.

For a campaign gaffe to really count as bad it needs to have the same relationship to a candidate's election prospects as the Titanic and an iceberg: everybody rushes for the lifeboats.

A wealthy oilman and "good ol' boy" who makes JR Ewing seem like a kitten, Williams was the Republican candidate for Texas governor in 1990. Running against the Democratic nominee Ann Richards, Williams's well-funded campaign raced to double-digit leads in the polls, despite his penchant for comparing rape to bad weather – "If it's inevitable, just relax and enjoy it" – and admissions that he had visited brothels in Mexico.

And then the wheels fell off.

Williams had avoided facing Richards in a debate. But his gaffe happened in a live, in-depth interview hosted by Dallas television stations.

As related by Molly Ivens, Williams mentioned that he had already voted by absentee ballot. Then the interviewer asked about his stance on a referendum question included on that year's ballot:

Interviewer: What's your stand on Proposition One?

Williams: Which one is that?

Interviewer: The only one on the ballot.

Even after it was explained to him, Williams still had no idea what his position was.

Interviewer: But haven't you already voted? You told us you voted absentee. Don't you remember how you voted?

Williams: I just voted on that the way my wife told me to, she knew what it was.

The obvious riposte was that his wife Modesta should have been running for governor.

Williams lost, narrowly, to Richards – who would be defeated four years later by a relatively gaffe-free George Bush.